Method for battery cell of novel structure

ABSTRACT

Disclosed herein is a method of manufacturing a battery cell having an electrode assembly of a cathode/separator/anode structure disposed in a battery case made of aluminum or an aluminum alloy together with an electrolyte in a sealed state, the method including (a) anodizing an entire surface of the battery case in a state in which a connection opening section, to which charge pins used to activate the battery cell are connected, is formed at a bottom of the battery case, (b) mounting the electrode assembly in the battery case and connecting a cap plate to an open upper end of the battery case by laser welding, (c) injecting an electrolyte through an electrolyte injection port of the cap plate and activating the battery cell, and (d) replenishing the electrolyte and sealing the electrolyte injection port.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT International Application No.PCT/KR2013/000582 filed on Jan. 25, 2013, which claims priority under 35U.S.C 119(a) to Application No. 10-2012-0012096 filed on Feb. 7, 2012 inthe Republic of Korea, all of which are hereby expressly incorporated byreference into the present application

TECHNICAL FIELD

The present invention relates to a method of manufacturing a batterycell having a novel structure, and, more particularly, to a method ofmanufacturing a battery cell having an electrode assembly disposed in abattery case made of aluminum or an aluminum alloy together with anelectrolyte in a sealed state, the method including (a) anodizing anentire surface of the battery case in a state in which a connectionopening section, to which charge pins used to activate the battery cellare connected, is formed at a bottom of the battery case, (b) mountingthe electrode assembly in the battery case and connecting a cap plate toan open upper end of the battery case by laser welding, (c) injecting anelectrolyte through an electrolyte injection port of the cap plate andactivating the battery cell, and (d) replenishing the electrolyte andsealing the electrolyte injection port.

BACKGROUND ART

As mobile devices have been increasingly developed, and the demand forsuch mobile devices has increased, the demand for secondary batteries asan energy source for the mobile devices has also sharply increased.Accordingly, much research on secondary batteries satisfying variousneeds has been carried out.

In terms of the material for batteries, the demand for lithium secondarybatteries, such as lithium ion polymer batteries, having high energydensity, discharge voltage, and output stability is very high. In termsof the shape of batteries, the demand for prismatic batteries orpouch-shaped batteries, which are thin enough to be applied to products,such as mobile phones, and may be used as batteries for a battery modulemanufactured by stacking the batteries with high integration is veryhigh.

An electrode assembly for secondary batteries, in which battery reactionis generated, is generally configured to have a structure in which acathode sheet having a cathode active material applied thereto, an anodesheet having an anode active material applied thereto, and a separatorare impregnated with an electrolyte. Based on the structure thereof, anelectrode assembly for secondary batteries is classified as a jelly-rolltype (wound type) electrode assembly and a stacked type electrodeassembly. The jelly-roll type electrode assembly or the stacked typeelectrode assembly is mounted in a prismatic metal case to manufacture aprismatic battery.

Generally, a prismatic battery is manufactured by mounting an electrodeassembly in a prismatic metal case, loading an upper insulator on theopen upper end of the prismatic metal case, connecting a cap plate tothe upper insulator by welding, injecting an electrolyte through anelectrolyte injection port, and sealing the electrolyte injection port.

At this time, a sealed portion of the battery case, in which the batterycell is mounted, is partially bent, and an insulative tape is attachedto it or a barcode is printed on it. However, this process is verycomplicated.

Also, when external impact is applied to a battery pack, a protectioncircuit module (PCM) may be damaged or dimensional stability of thebattery pack may be greatly lowered due to the use of the insulativetapes, which exhibit low mechanical strength.

In order to solve the above problems, therefore, surface treatment maybe carried out with respect to the battery case, or a cover havingpredetermined strength may be mounted to the battery case. In this case,however, welding may not be satisfactorily carried out due to thesurface treatment carried out with respect to the battery case when thecap plate is connected to the open upper end of the battery case bylaser welding.

Meanwhile, during mass production of a secondary battery, battery cellsare temporarily mounted in a charging and discharging device such thatthe battery cells are charged for activation at a step of placing thebattery cells in a pack case, and then the secondary battery ismanufactured as a battery pack, which is shipped. Connection terminalsof the charging and discharging device, which contact electrodeterminals of each battery cell to charge and discharge the battery cell,are generally formed in the shape of a pin. According to automatic massproduction, the connection terminals come into contact with theelectrode terminals of the battery cell to charge the battery cell andare then separated from the electrode terminals of the battery cellwithin a short time.

At this time, when the surface of the battery case is treated aspreviously described, the connection of the electrode terminals andcharge and discharge are not satisfactorily, achieved at one side atwhich the electrode pin is formed.

Also, various kinds of combustible a materials are contained in alithium secondary battery. As a result, the lithium secondary batterymay be heated or explode due to overcharge of the lithium secondarybattery, overcurrent in the lithium secondary battery, or other externalphysical impact applied to the lithium secondary battery. That is, thesafety of the lithium secondary battery is very low. Consequently,safety elements, such as a positive temperature coefficient (PTC)element and a protection circuit module (PCM), to effectively control anabnormal state of the lithium secondary battery, such as overcharge ofthe lithium secondary battery or overcurrent in the lithium secondarybattery, are loaded on a battery cell in a state in which the safetyelements are connected to the battery cell.

Generally, the PCM is electrically connected to the battery cell viaconductive nickel plates by welding or soldering. That is, nickel platesare connected to electrode tabs of the PCB by welding or soldering, andthe nickel plates are connected to electrode terminals of the batterycell by welding or soldering. In this way, the PCM is connected to thebattery cell to manufacture a battery pack.

It is required for the safety elements, including the PCM, to bemaintained in electrical connection with the electrode terminals of thebattery cell and, at the same time, to be electrically isolated fromother parts of the battery cell. To this end, a plurality of insulativemounting members or other parts is necessary, which complicates anassembly process of the battery pack. In particular, the sum of theheight of the PCM and the height of the insulative cap generally reaches3 mm with the result that a space necessary to receive the battery cellis reduced.

Consequently, there is a high necessity for a bus bar assembly having anovel structure that is capable of improving durability of a batterycase and easily performing connection of charge pins and charge anddischarge during activation while solving the above-mentionedconventional problems.

DISCLOSURE Technical Problem

Therefore, the present invention has been made to solve the aboveproblems and other technical problems that have yet to be resolved.

Specifically, it is an object of the present invention to provide amethod of anodizing the entire surface of a battery case in a state inwhich a connection opening section is formed at the bottom of thebattery case to easily perform the connection of charge pins.

It is another object of the present invention to provide a secondarybattery pack, the number of parts of which is reduced using the abovemethod, the assembly process of which is simplified, and which has abattery capacity greater than that of other battery packs having thesame standard.

Technical Solution

In accordance with one aspect of the present invention, the above andother objects can be accomplished by the provision of a method ofmanufacturing a battery cell having an electrode assembly of acathode/separator/anode structure disposed in a battery case made ofaluminum or an aluminum alloy together with an electrolyte in a sealedstate, the method including (a) anodizing an entire surface of thebattery case in a state in which a connection opening section, to whichcharge pins used to activate the battery cell are connected, is formedat a bottom of the battery case, (b) mounting the electrode assembly inthe battery case and connecting a cap plate to an open upper end of thebattery case by laser welding, (c) injecting an electrolyte through anelectrolyte injection port of the cap plate and activating the batterycell, and (d) replenishing the electrolyte- and sealing the electrolyteinjection port.

In the method of manufacturing the battery cell according to the presentinvention, therefore, the connection opening section is provided at thebottom of the battery case before the entire surface of the battery caseis anodized. Consequently, it is possible to easily achieve connectionbetween the electrode terminals and the charge pins.

In a concrete example, the step (a) may include (a1) a defatting processof dipping the battery case in a defatting solution, drawing the batterycase from the defatting solution, and washing the battery case in water,(a2) an acid cleaning process of dipping the battery case in an acidcleaning solution, drawing the battery case from the acid cleaningsolution, and washing the battery case in water, and (a3) an anodizingprocess of anodizing the surface of the battery case.

That is, durability and corrosion resistance of the battery case areimproved through anodizing of the battery case. Also, dyeing of thebattery case is possible due to small porosity and fiber propertythereof, thereby improving wear resistance and utility of the batterycase.

The shape of the connection opening section is not particularlyrestricted so long as the connection opening section corresponds to thecharge pins. For example, the connection opening section may be formedin a circular, oval, or polygonal shape in plan.

The method of forming the connection opening section is not particularlyrestricted. For example, the connection opening section may be formed byanodizing the battery case in a state in which an insulation material isapplied to a portion of the bottom of the battery case or an insulatoror an insulation tape is mounted or attached to a portion of the bottomof the battery case and removing the insulation material, the insulator,or the insulation tape.

According to circumstances, the method may further include sealing theconnection opening section using an insulation member after the step(d), thereby protecting the battery cell and maintaining electricalinsulation of the battery cell.

The material for the insulation member is not particularly restricted solong as the insulation member protects the connection opening sectionfrom the outside and maintains electrical insulation of the connectionopening section. Preferably, the insulation member is at least oneselected from a group consisting of an insulation tape, glue, andcoating.

In a preferred example, the battery cell activation process may beperformed in a state in which the first charge pin is connected to anupper electrode terminal of the cap plate and the second charge pin isconnected to the connection opening section of the battery case.

Consequently, effective charge may be achieved based on stable contactof the second charge pin. i.e. a cathode pin exhibiting cathodepolarity.

In another preferred example, the anodizing of the step (a) may becarried out in a state in which an uncoated margin section having apredetermined size is formed so as to extend downward from an outercircumference of the upper end of the battery case. Consequently, it ispossible to easily connect the cap plate to the open upper end of thebattery case by laser welding.

The uncoated margin section may extend downward from the outercircumference of the upper end of the battery case by a length of 0.5 to5 mm. If the length of the uncoated margin section is too long, it maybe difficult to achieve desired durability of the battery case based onsurface treatment, which is not preferable. On the other hand, if thelength of the uncoated margin section is too short, it may not bepossible to easily carry out laser welding, which is not preferable.

The method of forming the uncoated margin section is not particularlyrestricted. For example, the uncoated margin section may be formed byanodizing the battery case in a state in which an insulation material isapplied to the battery case or an insulator or an insulation tape ismounted or attached to the battery case and removing the insulationmaterial, the insulator, or the insulation tape.

The laser welding of the step (b) may be changed according to processconditions. Preferably, the laser welding of the step (h) is carried outalong the outer circumference of the battery cell above the cap plate.

In accordance with another aspect of the present invention, there isprovided a battery cell manufactured using the above method. The batterycell may have first and second electrode terminals formed at the topthereof.

In accordance with a further aspect of the present invention, there isprovided a secondary battery pack including the above battery cell.Specifically, the secondary battery pack according to the presentinvention includes the above battery cell, an insulative mounting memberhaving an opening, through which a second electrode terminal of thebattery cell is exposed, the insulative mounting member being mounted toa top of the battery cell, a protection circuit module (PCM) including aprotection circuit board (PCB), having a protection circuit, loaded onthe insulative mounting member, a connection member (A) connected to afirst electrode terminal of the battery cell, and a connection member(B) connected to the second electrode terminal of the battery cell via asafety element, the PCB being provided with a through hole, throughwhich the connection member (B) is exposed, and an insulative capcoupled to the upper end of the battery cell to surround the insulativemounting member in a state in which the connection members and theprotection circuit board are loaded on the insulative cap, wherein thesum of the height of the PCM and the height of the insulative cap is 0.6mm or less.

That is, in the secondary battery pack according to the presentinvention, the connection member (B), exposed through the through holeof the PCB, is electrically connected to the second electrode terminalof the battery cell via the PTC element from the above, and theconnection member (A) is electrically connected to the first electrodeterminal of the battery cell, in a state in which the PCM is loaded onthe insulative mounting member. Consequently, electrical connection isachieved using a simple connection method. Also, the assembly operationis easily performed, thereby greatly improving manufacturing efficiency.

Also, the connection member (A) extending from one end of the PCM is notbent, and the connection member (B) does not need an additional loadingspace. Consequently, it is possible to minimize a dead space, caused asthe connection members are bent for electrical connection of the safetyelement in the conventional art, and to minimize the sum of the heightof the PCM and the height of the insulative cap, thereby manufacturing asecondary battery pack having higher energy density than other secondarybattery packs having the same standard.

In a preferred example, the second electrode terminal may be an anodeterminal, and the first electrode terminal may be a cathode terminal.For example, a prismatic battery cell is configured to have a structurein which an electrode terminal protruding from the top of the batterycell and a battery case of the battery cell form an anode terminal and acathode terminal, respectively, and an insulation member is disposedbetween the anode terminal and the cathode terminal to insulate theanode terminal and the cathode terminal from each other. In thestructure of the prismatic battery cell, therefore, the second electrodeterminal may be an anode terminal protruding from the top of the batterycase, and the first electrode terminal may be a cathode terminal formedat the top of the battery case excluding the anode terminal.

Coupling (electrical connection) between the connection members and thePCM may be achieved using various methods. Preferably, the connectionmembers may be coupled to the bottom of the PCB using surface mounttechnology (SMT). The SMT prevents paste from remaining at the bottom ofthe PCB during soldering or the bottom of the PCB from being damage dueto heat during welding. Also, the SMT achieved accurate and reliablecoupling as compared with a conventional welding or soldering method.For reference, the SMT is widely used to mount surface mount type partson an electronic board, such as a printed circuit board (PCB).

In a preferred example, the connection member (B) may be coupled to thebottom of the through hole of the PCB. That is, the connection member(B) can be coupled to the safety element connected to the secondelectrode terminal through the through hole, thereby further simplifyingthe assembly process and minimizing the thickness of the PCM.

The safety element is an element, which is broken during conduction ofovercurrent or the resistance of which increases with the increase oftemperature. Preferably, the safety element is positive temperaturecoefficient (PTC) element. The connection member (B) coupled to the PTCelement serves to interrupt current at the upper end of the battery packwhen the temperature of the battery pack abruptly rises due to aninternal short circuit or the like. However, the safety element is notlimited to the PTC element. For example, a bimetal or a fuse may be usedas the safety element.

In the above structure, the PTC element may include a PTC body, a PCMcoupling part coupled to a top of the PTC body, and a battery cellcoupling part coupled to a bottom of the PTC body, and the PCM couplingpart may be coupled to the connection member (B) through the throughhole of the PCB.

Meanwhile, one end of the connection member (A) may be coupled to abottom of the PCB in a state in which the end of the connection member(A) extends longer than an outer circumference of the PCB such that theend of the connection member (A) is exposed upward. Preferably, theconnection member (A) has a thickness less than that of the insulativemounting member. Consequently, it is possible to easily secure a spacenecessary to locate the connection member (A) between one end of the PCMand one end of the top of the battery cell.

In another preferred example, the secondary battery pack may furtherinclude an auxiliary mounting member having one end coupled to a bottomof the PCB and the other end coupled to the top of the battery cell isprovided such that the PCB is stably mounted to the battery cell.

Specifically, the auxiliary mounting member may be coupled to a positionopposite to the connection member (A), and the auxiliary mounting membermay be coupled to the bottom of the PCB in a state in which theauxiliary mounting member extends longer than the outer circumference ofthe PCB such that one end of the auxiliary mounting member is exposedupward. Consequently, the auxiliary mounting member is stably fixed tothe PCB while minimizing a dead space.

The material for the auxiliary mounting member is not particularlyrestricted. Preferably, the auxiliary mounting member is formed of ametal plate, such as a nickel plate.

The coupling of the insulative mounting member to the top of the batterycase may be achieved, for example, by bonding, thereby achievingeasiness in assembly process of the battery pack and securing stablecoupling state.

The insulative cap may have a predetermined height sufficient for atleast a portion of the insulative cap to surround the outercircumference of the upper end of the battery cell in a state in whichthe insulative cap is mounted to the battery cell. Preferably, theinsulative cap has a height of 0.4 mm or less. Consequently, the heightof the insulative cap is minimized as compared with the height of aconventional insulative cap, and therefore, it is possible tomanufacture a secondary battery pack having higher energy density thanother secondary battery packs having the same standard.

The secondary battery pack according to the present invention may bevariously applied irrespective of the kind or external shape of thebattery cell. Preferably, the secondary battery pack according to thepresent invention is applied to a battery pack including a prismaticsecondary battery as a battery cell.

Effects of the Invention

As is apparent from the above description, in a battery cell accordingto the present invention, the entire surface of a battery case isanodized in a state in which a connection opening section is provided atthe bottom of the battery case and an uncoated margin section isprovided at the upper end of the battery case, thereby improvingdurability of the battery cell and easily performing connection ofcharge pins and laser welding of a cap plate.

Also, in a secondary battery pack including the battery cell with theabove stated construction, the sum of the height of a PCM and the heightof an insulative cap is minimized, and therefore, it is possible toincrease a battery capacity as compared with other battery packs havingthe same standard.

DESCRIPTION OF DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a front view showing a battery cell according to an embodimentof the present invention to which connection pins, which are used duringa charging process to activate the battery cell, are connected;

FIG. 2 is an exploded perspective view showing a battery cell, ananodized part, and an insulation tape of a secondary battery packaccording to an embodiment of the present invention;

FIG. 3 is a partial perspective view showing the bottom of the batterycell of FIG. 2;

FIG. 4 is a partial perspective view showing the upper end of thebattery cell according to the embodiment of the present invention;

FIG. 5 is a partial side view showing the upper end of the battery cellof FIG. 4;

FIG. 6 is an exploded perspective view showing the upper end of abattery cell and an insulative cap, on which an insulative mountingmember is loaded, of a secondary battery pack according to anotherembodiment of the present invention;

FIG. 7 is a partially enlarged side view of FIG. 6;

FIG. 8 is a partial perspective view showing a state in which theinsulative mounting member is mounted to the upper end of the batterycell of FIG. 6;

FIG. 9 is a partial perspective view showing a state in which aprotection circuit module (PCM) is mounted at the structure of FIG. 8;and

FIG. 10 is a partial perspective view showing a state in which theinsulative cap is mounted at the structure of FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

Now, preferred embodiments of the present invention will be described indetail with reference to the accompanying drawings. It should be noted,however, that the scope of the present invention is not limited by theillustrated embodiments.

FIG. 1 is a front view showing a battery cell to which connection pins,which are used during a charging process to activate the battery cell,are connected, FIG. 2 is an exploded perspective view showing thebattery cell, an anodized part, and an insulation tape, FIG. 3 is apartial perspective view showing the bottom of the battery cell, andFIG. 4 is a partial perspective view showing the upper end of thebattery cell.

Referring to these drawings, a battery cell 110 having an electrodeassembly of a cathode/separator/anode structure disposed in a batterycase 150 made of aluminum together with an electrolyte in a sealed stateis manufactured as follows. First, the entire surface of the batterycase 150 is anodized (155) in a state in which a connection openingsection 162, to which charge pins 160 and 161 used to activate thebattery cell 110 are connected, is formed at the bottom 159 of thebattery case 150. Subsequently, the electrode assembly is mounted in thebattery case 150, a cap plate 152 is connected to the open upper end ofthe battery case 150 by laser welding, an electrolyte is injectedthrough an electrolyte injection port 153 of the cap plate 152, and thebattery cell is activated. Subsequently, the electrolyte is replenished,and then the electrolyte injection port 153 is sealed.

The connection opening section 162 is formed in a quadrangular shape inplan. Alternatively, the connection opening section 162 may be formed invarious shapes in plan.

Also, the connection opening section 162 is formed by anodizing (155)the battery case 150 in a state in which an insulation material (notshown) is applied to a portion of the bottom of the battery case 150 andremoving the insulation material.

Finally, the connection opening section 162 is sealed using aninsulation member 165, such as an insulation tape.

The battery cell activation process is performed in a state in which thefirst charge pin 160 is connected to an upper electrode terminal 111 ofthe cap plate 152 and the second charge pin 161 is connected to theconnection opening section 162 of the battery case 150.

Consequently, the connection of the second charge pin 161 is easilyachieved by the provision of the connection opening section 162.

FIG. 5 is a partial side view showing the upper end of the battery ellof FIG. 4.

Referring to FIG. 5 together with FIGS. 1 to 4, the entire surface ofthe battery case 150 is anodized (155) (see FIG. 2) in a state in whichan uncoated margin section 151 having a length h of about 3 mm isprovided downward from the outer circumference of the upper end of thebattery case 150. The uncoated margin section 151 is formed by anodizingthe battery case 150 in a state in which an insulation material (notshown) is temporarily applied to the battery case 150 and removing theinsulation material.

Laser welding is carried out along the outer circumference of thebattery cell 110 above the cap plate 152 (see an arrow shown in FIG. 4).The laser welding of a cap assembly is easily carried out by theprovision of the uncoated margin section 151.

FIG. 6 is an exploded perspective view showing the upper end of abattery cell and an insulative cap, on which an insulative mountingmember is loaded, of a secondary battery pack according to an embodimentof the present invention, FIG. 7 is a partially enlarged side view ofFIG. 6, FIG. 8 is a partial perspective view showing a state in whichthe insulative mounting member is mounted to the upper end of thebattery cell, FIG. 9 is a partial perspective view showing a state inwhich a protection circuit module (PCM) is mounted to the upper end ofthe battery cell, and FIG. 10 is a partial perspective view showing astate in which the insulative cap is mounted to the upper end of thebattery cell.

Referring to these drawings, a secondary battery pack 100 is configuredto have a structure including a battery cell 110, an electricallyinsulative mounting member 120 mounted to the top of the battery cell110, a PCM 130, and an insulative cap 140 mounted to the upper end ofthe battery cell 110 while surrounding the insulative mounting member120.

The battery cell 110 is configured to have a structure in which anelectrode assembly of a cathode/separator/anode, structure is mounted ina battery case 150 made of aluminum together with an electrolyte in asealed state, an anode terminal 111 protrudes from the middle of the topof the battery cell 110, and a cathode terminal 112 is formed at the topof the battery cell 110 excluding the anode terminal 111.

The insulative mounting member 120 is provided with an opening 121,through which the anode terminal 111 of the battery cell is exposed.

The PCM 130 includes a protection circuit board (PCB) 133 loaded on theinsulative mounting member 120, the PCB 133 having a protection circuit,a connection member 132 connected to the cathode terminal 112, and aconnection member 136 connected to the anode terminal 111 via a positivetemperature coefficient (PTC) element 134. The PCB 133 is provided witha through hole 137, through which the connection member 136 is exposed.

The connection member 36 is coupled to the bottom of the through hole137 of the PCB 133.

Referring to FIG. 8, the PTC element 134 includes a PTC body 1341, a PCMcoupling part 1342 coupled to the top of the PTC body 1341, and abattery cell coupling part 1343 coupled to the bottom of the PTC body1341. The PCM coupling part 1342 is coupled to the connection member 136through the through hole 137.

Meanwhile, one end of the connection member 132 is coupled to the bottomof the PCB 133 by surface mount technology (SMT) in a state in which theend of the connection member 132 extends longer than the outercircumference of the PCB 133 such that the end of the connection member132 is exposed upward.

An auxiliary mounting member 135, formed of a nickel plate, having oneend coupled to the bottom of the PCB 133 and the other end coupled tothe top of the battery cell 110 is provided such that the PCB 133 can bestably mounted to the battery cell 110. The auxiliary mounting member135 is coupled to a position opposite to the connection member 132.

The insulative cap 140 is made of an electrically insulation material.The insulative cap 140 is formed to surround the insulative mountingmember 120 in a state in which the connection members 132 and 136 andthe protection circuit board 133 are loaded on the insulative cap 140.

Also, the insulative cap 140 is coupled to the top of the battery cell110 by bonding. The insulative cap 140 has a height of about 0.4 mm orless.

In the secondary battery pack 100 according to the present invention,therefore, the connection member 136, exposed through the through hole137 of the PCB 133, is electrically connected to the anode terminal 111of the battery cell 110 via the PTC element 134 from the above, and theconnection member 132 is electrically connected to the cathode terminal112 of the battery cell 110, in a state in which the PCM 130 is loadedon the insulative mounting member 120. Consequently, electricalconnection is achieved using a simple connection method. Also, the sumof the height of the PCM 130 and the height of the insulative cap 140 isabout 0.6 mm or less. Consequently, it is possible to manufacture asecondary battery pack having higher energy density than other secondarybattery packs having the same standard.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

The invention claimed is:
 1. A method of manufacturing a battery cellhaving an electrode assembly of a cathode/separator/anode structuredisposed in a battery case made of aluminum or an aluminum alloytogether with an electrolyte in a sealed state, the method comprising:(a) anodizing an entire surface of the battery case in a state in whicha connection opening section, to which charge pins used to activate thebattery cell are connected, is formed at a bottom of the battery case;(b) mounting the electrode assembly in the battery case and connecting acap plate to an open upper end of the battery case by laser welding; (c)injecting an electrolyte through an electrolyte injection port of thecap plate and activating the battery cell; and (d) replenishing theelectrolyte and sealing the electrolyte injection port.
 2. The methodaccording to claim 1, wherein the step (a) comprises: (a1) a defattingprocess of dipping the battery case in a defatting solution, drawing thebattery case from the defatting solution, and washing the battery casein water; (a2) an acid cleaning process of dipping the battery case inan acid cleaning solution, drawing the battery case from the acidcleaning solution, and washing the battery case in water; and (a3) ananodizing process of anodizing the surface of the battery case.
 3. Themethod according to claim 1, wherein the connection opening section isformed in a circular or polygonal shape in plan.
 4. The method accordingto claim 1, wherein the connection opening section is formed byanodizing the battery case in a state in which an insulation material isapplied to a portion of the bottom of the battery case or an insulatoror an insulation tape is mounted or attached to a portion of the bottomof the battery case and removing the insulation material, the insulator,or the insulation tape.
 5. The method according to claim 1, furthercomprising sealing the connection opening section using an insulationmember after the step (d).
 6. The method according to claim 5, whereinthe insulation member is at least one selected from a group consistingof an insulation tape, glue, and coating.
 7. The method according toclaim 1, wherein the battery cell activation process is performed in astate in which the first charge pin is connected to an upper electrodeterminal of the cap plate and the second charge pin is connected to theconnection opening section of the battery case.
 8. The method accordingto claim 1, wherein the anodizing of the step (a) is carried out in astate in which an uncoated margin section having a predetermined size isformed so as to extend downward from an outer circumference of the upperend of the battery case.
 9. The method according to claim 8, wherein theuncoated margin section extends downward from the outer circumference ofthe upper end of the battery case by a length of 0.5to 5 mm.
 10. Themethod according to claim 8, wherein the uncoated margin section isformed by anodizing the battery case in a state in which an insulationmaterial is applied to the battery case or an insulator or an insulationtape is mounted or attached to the battery case and removing theinsulation material, the insulator, or the insulation tape.
 11. Themethod according to claim 1, wherein the laser welding of the step (b)is carried out along an outer circumference of the battery cell abovethe cap plate.
 12. A battery cell manufactured using a method accordingto claim
 1. 13. The battery cell according to claim 12, wherein thebattery cell has first and second electrode terminals formed at a topthereof.
 14. A secondary battery pack comprising: a battery cellaccording to claim 12; an insulative mounting member having an opening,through which a second electrode terminal of the battery cell isexposed, the insulative mounting member being mounted to a top of thebattery cell; a protection circuit module (PCM) comprising a protectioncircuit board (PCB), having a protection circuit, loaded on theinsulative mounting member, a connection member (A) connected to a firstelectrode terminal of the battery cell, and a connection member (B)connected to the second electrode terminal of the battery cell via asafety element, the PCB being provided with a through hole, throughwhich the connection member (B) is exposed; and an insulative capcoupled to an upper end of the battery cell to surround the insulativemounting member in a state in which the connection members and theprotection circuit board are loaded on the insulative cap, wherein a sumof a height of the PCM and a height of the insulative cap is 0.6 mm orless.
 15. The secondary battery pack according to claim 14, wherein thesecond electrode terminal is an anode terminal protruding from a middleof the top of the battery cell, and the first electrode terminal is acathode terminal formed at the top of the battery cell excluding theanode terminal.
 16. The secondary battery pack according to claim 14,wherein the connection members are coupled to a bottom of the PCB usingsurface mount technology (SMT).
 17. The secondary battery pack accordingto claim 14, wherein the connection member (B) is coupled to a bottom ofthe through hole of the PCB.
 18. The secondary battery pack according toclaim 14, wherein the safety element is a positive temperaturecoefficient (PTC) element, the PTC element comprising a PTC body, a PCMcoupling part coupled to a top of the PTC body, and a battery cellcoupling part coupled to a bottom of the PTC body, the PCM coupling partbeing coupled to the connection member (B) through the through hole ofthe PCB.
 19. The secondary battery pack according to claim 14, whereinone end of the connection member (A) is coupled to a bottom of the PCBin a state in which the end of the connection member (A) extends longerthan an outer circumference of the PCB such that the end of theconnection member (A) is exposed upward.
 20. The secondary battery packaccording to claim 14, further comprising an auxiliary mounting memberhaving one end coupled to a bottom of the PCB and the other end coupledto the top of the battery cell is provided such that the PCB is stablymounted to the battery cell.
 21. The secondary battery pack according toclaim 20, wherein the auxiliary mounting member is coupled to a positionopposite to the connection member (A).
 22. The secondary battery packaccording to claim 20, wherein the auxiliary mounting member is coupledto the bottom of the PCB in a state in which the auxiliary mountingmember extends longer than an outer circumference of the PCB such thatone end of the auxiliary mounting member is exposed upward.